1. Field of the Invention
The present invention relates to a polishing composition having a specified viscosity, a roll-off reducing agent and a polishing composition using the roll-off reducing agent. Furthermore, the present invention relates to a process for producing a substrate comprising applying the polishing composition to the substrate, and a process for reducing roll-off of a substrate.
2. Discussion of the Related Art
Over the years, a demand for a technique for further increasing the capacity of the hard discs has become greater. As a leading means for increasing the capacity of the hard discs, there has been considered a means of producing a substrate capable of recording data even to its outer periphery by reducing roll-off (edge rounding of end side of a substrate) caused in the polishing process. For instance, various mechanical polishing conditions, such as making a polishing pad more rigid, and making a polishing load smaller, have been studied in order to produce a substrate having a reduced roll-off. However, although a certain extent of an effect is obtained by reducing roll-off with these mechanical polishing conditions, the effect has not yet been satisfactory. Also, from the viewpoint of reducing roll-off with the polishing composition used in the polishing step, the use of a specified organic acid represented by an organic acid having hydroxyl group (Japanese Patent Laid-Open No. 2002-12857), the use of sol product of aluminum salt (Japanese Patent Laid-Open No. 2002-20732), the use of polyalkylene oxide compound (Japanese Patent Laid-Open No. 2002-167575), and the like have been proposed. However, roll-off cannot be said to be satisfactorily reduced.